Mouse model for central nervous system Neospora caninum infections.

Neospora caninum is a protozoan parasite that causes severe disease in transplacentally infected dogs and abortions in domestic ruminants. Rodent models of neosporosis rely on treatment of hosts with methylprednisolone acetate (MPA) to enhance infections. The present study reports the development of an inbred BALB/c mouse model that results in central nervous system neosporosis in the absence of MPA treatment. Seven of 12 BALB/c mice died 26-70 days after subcutaneous (s.c.) inoculation with tachyzoites of the NC-1 strain of N. caninum, and none of 12 BALB/c mice died after s.c. inoculation with tachyzoites of the NC-3 strain. None of 8 HSD:ICR mice (4 mice, NC-1 strain; 4 mice, NC-3 strain) developed clinical neosporosis or died after s.c. inoculation with tachyzoites. Control BALB/c (2) and HSD:ICR (2) mice s.c. inoculated with Hanks' balanced salt solution did not develop clinical signs of disease. Some mice in all N. caninum-inoculated groups had brain lesions, but significantly (P < 0.05) more BALB/c mice inoculated with the NC-1 strain had brain lesions.